15" Tannoy dual concentrics in original Imperials?10/09/07 at 18:49:16

Hi all, my first post here. Some time ago I scored a pair of cabinets, 60" h x 36" w x 24" deep, that I believe were built from original Jensen plans. I'll put some images in the next message.

I just cut out 3 sets of baffle boards to try different sets of drivers. I tried a friend's pair of Tannoy drivers (HPD385, I think) in these a long time ago and we were both floored, so the trial lineup (most appropriate of what I happen to have) includes:

JBL 2220BTannoy 3836Tannoy gold 15" (not sure of model details - like HPD 385 but w/o the strips on the back of the cone)

Just for grins, I might pull the drivers out of a pair of Tannoy DMT15 IIs that I have... But I see almost nothing about people trying Tannoy 15"s in these cabinets. That seems odd, because the specs I see on some of the drivers (see http://44bx.com/tannoy/Tannoy_ts.html) look good! For example, the HPD 385A has an Fs of 22, Qts of 0.18, efficiency of 94.3. Vas is HIGH at 483L, though.

Has anyone here been down this road?

I'm a big fan of the dual concentric / point source coherence of the Tannoy drivers, and like very much my DMT 15s, but my hope is that the right dual concentrics in these cabinets will give me the big dynamics and convincing bottom end while maintaining the coherence I like for 100 hz to the top. And my hope is also that this solution will mean not needing a big compression driver and horn.

But if I'm wrong, and I miss that BIG SOUND for the top half of the music, I'm open to the idea of a really good horn + compression driver for the top.

I'll try to insert an image of the drivers that sounded so promising, using the original baffle boards and Tannoy crossover:

The actual construction is of 3/4" plywood, double-thck in many places, thorougly glued and screwed. Interestingly, when I got them, they had Stephens Trusonics in the 15" slot, but the builder had added a Calrad midrange and University tweeter too. It was complicated. The plans recommended a Jensen 610G triaxial. It would be nice to try that in there, but .... I'm two short of a pair. ;)

Last night I got a pair of Tannoy 15" mounted and biamped, using Apogee DAC, Intact Audio autoformer volume control, Heathkit XO-1 crossovers, deHavilland Aries 845 amps, and a pair of SE EL-34 amps. This is not some final setup by a long shot -- just throwing together what I had around.

The drivers seem to be early HPD 385's or close to it. I posted photos on the tannoy yahoo group, and didn't get the definitive word, but here's what matters:

they sound great in the Jensen Imperial cabinets!

I don't know how much I believe in "warm-up" or time for equipment to come around after long disuse, but with the drivers and crossovers unused for YEARS prior, there DID some to be some really noticeable iimprovement from the first cut to the last.

I threw this together with lousy cables, 14ga house wiring, clip leads and alligator clips, but it was EASY to overlook all that. Man, when I get this all dialed in ... watch out!

Okay, next step in getting to the next level: I scored a pair of Tannoy GRF's from around 1971, consecutive serial numbers, from the original owner -- and that means there's a pair of nice Monitor Golds in there! Just unloaded the speakers tonight, and now listening to them through some nice tubes. Definitely some magic there! Could leave these things alone and enjoy them as-is! They are the ones in the top right of the attached brochure.

I could sure use some help understanding what drivers work in the Jensen Imperials. From what little I know, the Tannoy Gold 15s should work well in there. See attached image, or see the easier to read the table version down on this page:http://www.hilberink.nl/codehans/tannoy38.htm

I can say one thing. Tannoy Monitor Gold 15"s in my cabinets are THE BOMB. I removed the drivers and crossovers from the GRF cabinets, and cut new baffle boards to use them in my imperial cabinets. Had to cut a 3/4" hole to get the crossover-to-driver plug through it, and then seal it up with plumber's putty, but now I can really compare the performance of these drivers and crossovers in a set of considerably larger backloaded horns.

WOW, this is the best biggest bass-ingest sound I EVER heard out of Tannoys. I'm using deHavilland Aries 845 amps, which can do 30 watts but are probably hitting 5. This is SERIOUSLY good. I'm amazed I still haven't come across anyone using vintage Tannoy dual concentrics in an imperial-type cabinet. Am I really making audio history here?!? I doubt it, but I know I've got something REALLY good going here.

My speaker buddy is telling me that eventually I'll figure out that the 1" Tannoy HF driver isn't enough to keep up with the big bottom end with these cabinets, and that could be true, but DAMN I've got something special to listen to while I figure it out!

Since hooking it up I've been too busy listening to take pictures, but here's a BEFORE picture:

They don't look like that now, but cosmetically they haven't improved much, either! I took out the 12" Calrad midrange from slanted horn mouth, but haven't yet cut out MDF circles to fill that hole! I will get to that soon though... That's only one of several things that are really WRONG, and if it didn't sound so good already I'd either give up or feel compelled to deal with it immediately. As it is, I just know that there is a long list of incremental fixes in the works.

I took out the Monitor Golds, and put in the Tannoy 3833 drivers used in the DMT 15 IIs. I used the DMT15 crossovers too. Still using the deHavilland 845 amps.

I thought the higher Qts of the 3833s would make for some sloppy bass, but they perform well in these Jensens. All in all, it's a balance not that different from in the DMT sound, except that dynamics and that whole coupling-with-the-room thing the Imperials do is jumped up a couple notches.

It's really very good. But without being able to fault anything, I find it is just less involving than the Monitor Golds are in the same cabinets. I kinda liked the idea that I could get all that magic with some readily-available, durable drivers like the 3833's, rather than through the Monitor Golds... but so far I can't say that's true. There's a CLEANER sound with the 3833's, but that could be as much the switchless new-parts crossover versus the old lotsa-moving-parts Monitor Gold crossovers. I intend to build a good alternative to the original crossover, which ought to be telling.

Yeah, I followed that auction... and then very recently there was one for a pair of Tannoy Westminsters, in Scottsdale AZ, but it was pulled, and might have been one of a series of scam Westminster auctions...

In any case, there is a strong resemblance between the backloaded horn designs of the Autograph, GRF Pro, Westminster & Court Imperial, and the Jensen and Decware Imperial: similar horn lengths, similar chamber behind driver, similar equivalent horn mouth size. (The GRF-R, which I wrote about in another thread, is a baby version, but good to 40 or so hornloaded hz.)

But here's what might be a SIGNIFICANT difference. The Jensen/Decware Imperial, and the GRF-R, have one single rectangular mouth at the bottom, as opposed to two very tall skinny mouths on either side. If part of the magic of the Jensen/Decware Imperial design is that it develops a BIG coherent soundwave below 350hz (or whatever), vs. whatever comes out of two tall skinny mouths, then I might know one thing I prefer about the sound of my ugly cabinets over the beautiful Autographs and Westminsters.

Or maybe it's sour grapes (justification about why I don't want what I can't have)